Ball bearings are sometimes used for transmitting an axial force, i.e. a force parellel to the central axis of the bearing. This applies in particular to clutch thrust bearings used in motor vechicles.
FR-A-2 898 951 discloses a clutch thrust bearing device in which a drive member is associated with a ball bearing, thus enabling a diaphragm of a clutch mechanism to be controlled. An annular member is fastened to the inner ring and has an axial portion of large diameter that is received with relatively small radial clearance in a central bore of the outer ring. The annular member co-operates with the outer ring to perform a sealing function, providing the respective axes of symmetry of the inner and outer rings remain in alignment. In the event of these axes coming out of alignment, the large-diameter axial portion of the annular member collides with the edge face of the bore in the outer ring on one side, while on the other side a relatively large space is left between the annular member and the outer ring, and that can give rise to pollution in the raceway chamber in which the balls are contained.
In a clutch thrust bearing, it can happen that the axis of the diaphragm clutch mechanism is not accurately in alignment with the axis of the outlet shaft from the gearbox, which can lead to high levels of stress on certain component parts of the clutch thrust bearing, to such an extent to limit the lifetime of that type of equipment. Alignment is lost between the above-mentioned axes when they intersect or when they no longer coincide, even while remaining parallel.
The annular member of FR-A-2 989 951 allows the drive element to move radially relative to the inner ring of the bearing, thereby making it possible to accommodate the situation in which the above-mentioned axes are parallel, but without coinciding. Nevertheless, that equipment is not effective when the axes intersect.
Because of the complexity of clutch mechanisms, where complexing has been increasing in particular since the emergence of double clutches, and also for economic reasons, the manufacturing tolerances for certain component parts of a clutch are tending to increase, such that the offset angle between the inlet and outlet axes of a clutch thrust bearing is tending to increase, so as to reach values that are relatively large. Under such circumstances, the equipment of FR-A-2 898 951 is not suitable.
DE-U-203 02 774 discloses a bearing having an inner ring and an outer ring with balls placed between them, and with swiveling being made possible by the balls rolling on the outer ring. Under such circumstances, a gap left between the inner ring and a metal part wedged on the outer ring presents a width that varies, thereby running the risk of the bearing becoming polluted.
The invention seeks more particularly to remedy those drawbacks by proposing a novel ball bearing suitable for use in a clutch thrust bearing and capable of accommodating misalignment between its inlet and outlet axes, while isolating the chamber containing the balls of the bearing from the outside.